tracking stolen iPhone via thief's iCloud account, IP address

I just had my Verizon iPhone stolen. I know it was stolen because it had full battery life and when I tried calling it, it was already off.

I believe i had Find My Phone enabled, but I did not have the screen locked with a pass code. So I'm assuming they will, if they haven't already, wiped the phone and taken out the SIM card. And are probably keeping it offline.

I guess I have a couple questions. If they happen to use it for themselves after wiping it and all that, can it be tracked to their iCloud account if they happen to log in with it? Even if all the data is removed and the SIM card.

Or can the phone somehow be tracked to their IP address if they connect it to their wifi network?

Find My Phone isn't resulting in anything and Apple more or less confirmed there was no other way to locate it. But both those scenarios seem reasonable to me.

And if they wipe the phone.. isn't it in some way still connected to my phone number through the Apple servers?

Thanks for any insight.